Electrical radiation apparatus



1933 u. SCHONFELD I A 321,543

ELECTRICAL RADIATION APPARATUS Filed March 25, 1931 Patented Aug. 8, 1933 ELECTRICAL RADIATIQN APPARATUS Ulrich Schiinfeld, Berlin-Pankow, Germany, as-

signor to Steatit-Magnesia Germany,

Berlin-Pankow, Germany Altiengesellschaft, a Corporation of Application March 25, 1931, .Serial No. 525,257,

and in Germany March 31, 1930 3 Claims. (01. 219-19 My invention relates to improvements in electrical radiation apparatus, and more particularly in radiation apparatus in which a resistance wire or wires are supported on an insulating plate of refractory material, and which are used for heating or cooking purposes. The object of the improvements is to provide an apparatus of this type in which the position of the resistance wire or wires relatively to each other and to the refractory base is not affected by heating the wires. With this object in view my invention consists in constructing the heating coil and the base so that the coil is clamped on the base by spring action. In carrying out the invention I construct the windings of the heating wire or coil in crescent form, the crescent-shaped windings embracing a rib or ribs projecting from the insulating base, and being held thereon by spring action.

For the purpose of explaining the invention several examples embodying the samehave been shown in the accompanying drawing, in which the same letters of reference have been used in all the views to indicate corresponding parts. In said drawing,

Fig. 1 is an elevation showing the radiation apparatus,

Fig. 2 is a top plan view of Fig. l,

Fig. 3 is a perspective view on an enlarged scale showing the resistance coil separate from the base,

Fig. i is an end elevation of the said coil,

Fig. 5 is a perspective view on an enlarged scale showing one of the coils illustrated in Figs. 1 to 4 and a portion of the base supporting the same,

Fig. 6 is a plan view showing a modification of the radiation apparatus, the heating coil being supported on a spiral rib,

Fig. 7 is a detail sectional elevationshowing a modification in which the heating coil has the form shown in Figs. 1 to 5, which coil is supported on a pair of ribs projecting from the base,

Fig. 8 is a similar sectional elevation showing another modification in which the rib supporting the heating coil is X-shaped in cross-section.

In the construction shown in Figs. 1 and 2 the radiation apparatus comprises a base plate a of ceramic material such as steatite, porcelain or the like, and four rectilinear bars I) disposed parallel toeach other and, preferably, made integral with the base plate (1. Thus the bars are in the form of ribs projecting from the base plate, and. they are reduced in thickness at their median parts. The ribs b provide supports for heating coils c which are made for example from a chromium nickel alloy.

As appears from Bags. 3 and 4, which show the heating coil in detail, the said coil consists of a helically wound wire. But the windings of the coil are not circular, as is usual, but they are bent into crescent shape, as is best shown in Fig. 4, each winding comprising two concentric portions 01 and c3 and rounded connecting portions c2, 02, the said winding being in shape similar 6 to an open ring. As appears from Fig. 3, each winding comprises an outer arc-shaped section .01 which extends in helical form from one side of the rib b to the opposite side thereof, where it is connected by the curved portion 02 with the inner are 03 which extends in helical form from the said side of the rib to the opposite side, and which at the said opposite side merges by a small curved portion 02 into the next large are 01, etc. The windings c1 and c3 respectively are disposed close to each other, sothat efiective heating is insured. I wish it to be understood that in the drawing the distance between adjacent coils is comparatively large merely for convenience in illustration, and that practically the said distance is considerably smaller.

The winding 0 embraces the enlarged head in of the rib b, the arc shaped portions 02 engaging the lateral recesses D1 of the rib. By elasticity of the sections 01, ca of the windings the curved portions c2 are pressed into the recesses in, so that the adjacent windings cannot be shifted longitudinally of the coil and the rib b when the wire is heated and expanded. Therefore the adjacent windings remain out of contact with each other, so that short circuits are avoided. Further, only a very small portion of each winding is covered by the head D2 of the rib b, so that the heating capacity is high.

The coil 0 shown in Fig. 3 may be manufactured by first manufacturing a circular or' oval coil, and thereafter bending the corresponding portions of the winding inwardly and into the form oi a 0, such bending being preferably effected while the wire is at red heat and pliable. In amodification of the method the windings are bent into C-form while the coil is being wound.

The crescent-shaped coil 0 is placed on the base a by passing the same on the rib b from one end thereof and longitudinally of the rib, so that the curved portions 02 engage in the recesses in. But if the elasticity of the coil is sufflcient it may be placed on the rib b2 from the top side thereof downwardly.

To the plate a clamping screws 12 are fixed to which the free ends of the coils c are secured, all the coils mounted on the ribs being connected in series. To the outer terminals d leading-in wires m are secured, as is shown in Fig. 2.

Instead of providing the base a with individual ribs disposed parallel to one another, I may provide the same with ribs which cross one another to provide a grate. Further, the ribs may be provided with longitudinal recesses or grooves.

In Fig. 6 I have shown a modification in which a circular base e is provided with a single spiral rib i, which rib is similar in cross-section to the ribs 1; shown in Figs. 1 to 5. On the said spiral rib a heating coil 0 is mounted which has the form of a crescent, a c, or an open ring, as has been described with reference to Figs. 1 to 5.

In lieu of the rib 1; formed on the base a and having the heating coil 0 clamped thereon I may provide a pair of spaced ribs g having beads 91 at their outer top ends, as is shown in Fig. 7, the said beads providing recesses g2 which are engaged by the curved portions 02 of the heating coils c.

In Fig. 8 I have shown a modification in which 7 the rib carrying the heating coil is X-shaped in cross -section, as is shown at h. The curved portions 02 of the heating coil 0 engage in the recesses hl provided by the arms of the rib h.

I claim: 1. A radiation apparatus, comprising a ,base

of insulating material in the form of a bar having longitudinal recesses at its sides, and a crescent-shaped heating coil engaging said recesses and held on said base by spring action, each turn of the heating coil comprising an inner and outer portion defining the outline of a crescent and connected to each other, the portions of each turn lying in substantially the same radial plane.

2. A radiation apparatus, comprising a base of insulating material and in the formof a bar having longitudinal recesses at its sides, and a crescent-shaped heating coil engaging said recesses and held on said base by spring action, said heating coil being composed of helically disposed windings each comprising an outer arc and an inner concentric arc, defining the outline of a crescent and connected together in reverse magnetic efiect, the portions of "each turn lying in substantially the same radial plane.

3. A radiation apparatus, comprising a base of insulating material and in the form of a bar having longitudinal recesses at its sides, and a crescent-shaped heating coil comprised of inner and outer superposed turns, the inner turns engaging said recesses and holding on said base by the spring action at their ends, said turns comprising substantially G-shaped windings arranged in zigzag.

ULRICH SCHONFELD. 

